According to the prior art, the most common structures to achieve an enhancement-mode AlGaN/GaN high electron mobility transistor (E-mode AlGaN/GaN HEMT) include: 1. Ga-face p-GaN gate E-mode HEMT structure, and 2. N-face Al(x)GaN gate E-mode HEMT structure. Nonetheless, as implied by their names, only the gate region will be p-GaN or Al(x)GaN.
The most common fabrication method is to use an AlGaN/GaN HEMT epitaxial structure capped with a p-GaN layer. The process starts by etching away p-GaN outside the p-GaN gate region using dry etching while maintaining the completeness of the thickness of the underlying AlGaN epitaxial layer. Because if the underlying AlGaN epitaxial layer is etched too much, two-dimensional electron gas (2DEG) will not be formed at the interface AlGaN/GaN of a Ga-face p-GaN gate E-mode HEMT structure. Thereby, the using dry etching is challenging because the etching depth is hard to control, plus nonuniformity in AlGaN thickness is also an uncontrollable variable.
Accordingly, to improve the above drawbacks, the present invention provides a novel epitaxial structure of Ga-face group III nitride, an active device formed by using the epitaxial structure, and the fabrication method for integration.